V1
Unzip and copy the Tuxkiller3 folder in the /usr/share/mdm/html-themes/.
Select Tuxkiller3 theme with the executable MDM setup HTML style.
There are five preset languages to date en, es, fr, it, pt, zh, ru in the file /usr/share/mdm/html-themes/Tuxkiller3/js/showdate2.js. You can add the following month and day lists.
There can choose an effect option for the icons at the bottom of the screen:
Magnifying icons similar to a dock.
Bouncing icons.
Fade.
Halo around the icons.
Replace an image with Reviews another.
Icons rotation -45 degrees.
RotationY icons.
Sonar.
Zoomin zoomout.
To select the desired effect, simply uncomment one of the lines corresponding to their choice of file /usr/share/mdm/html-themes/Tuxkiller3/index.html.
You can also change the message title rotating line 303 of file /usr/share/mdm/html-themes/Tuxkiller3/index.html.

StarSapphireKDE 1 (KDE Icon Theme)Based on NouveKDEGray by Tsujan. Word of warning, very heavy, will take a while to show up if installed through System Settings. Not recommended for lite installations, low RAM.

Velours (Plasma 4+5) 5.0 (Plasma Theme)Velours is a dark plasma theme with a fuzzy texture and monochromatic icons.
It draws inspiration from Caledonia by Malcer (which it was originally a fork of) and openSUSE by sumski.

Since v3.0, it contains only original artwork.

It might not fit everyone's use case. Don't hesitate to ask for specific missing parts if need be.

A new branch was created for Plasma 5! If you were already using Velours under Plasma 5, I suggest you switch to the new theme. Currently, the only difference is that the icons were reworked to better fit the system tray. If you are using Plasma 4, you can also try it out if you are experiencing blurry icons.

Known issue: The notification tray icon is incorrectly stretched to 28x28 instead of 22x22. I reported it and it is already corrected upstream.

changelog:9/7/15:
Added Plasma 5 branch with better system tray icons

20/6/15:
Added icons for media player system tray entry (in Plasma 5)

20/4/15:
The hover state of the task element was redesigned.
Selected item background gradient was softened.
Some icons were improved.

26/3/15 :
Moved to GitHub
Widget backgrounds were redesigned: the border radius went from 3px to 5px and a more opaque border was added. Other widgets were also remade/polished.
Many icons were redone and almost all of them now have dark borders to stay distinguishable against pale backgrounds.

19/01/15 v3 :
First complete release. All artwork from Caledonia has been replaced and the license changed from by-sa to by-nc-sa.